Short for Directory Harvest Attack, DHA is a type of malicious Internet attack where online spammers collect valid e-mail address and target those addresses in a spam attack or sell the lists of valid e-mail addresses to unscrupulous marketers. In a DHA attack, the spammer will select a domain name, for example, Webopedia.com. The spammer then sends an e-mail to any possible addresses within that domain name. If the e-mail server doe not reject the e-mail, the spammer knows it is a valid e-mail address and adds it to his target list.